Fluorescent lamp device with luminosity control

ABSTRACT

A fluorescent lamp device in which a DC power source of high voltage and small capacity is connected for maintaining a slight glow discharge within the lamp, a main current of the lamp being adjustably supplied from a main power source of large capacity and a rectifier is inserted into the main power circuit for blocking high voltages DC current flowing into the main circuit from the high-voltage source.

United States Patent 1111 3,603,841

[72] Inventors Heima Yamada [50] Field of Search 315/100 H, Kyoto; 1000,97, 105, 160, 169,100,101, 171, 176; Masashi Sangen, Kobe; Kazumasa Nomi, 313/212 Talmtsuki-shi, all of, Japan {21] Appl. No 802,036 [56] References Cited 22 Filed Feb. 25, 1969 UNITED STATES PATENTS I 1 Famed p 2,177,883 10/1939 Foulke 315 105 x I 8 Col'lmmw 2,311,543 2/1943 116m 315/160 x "P" 2,513,091 6/1950 Fl'OhOCk 315 212 x [321 1119681)! 3,066,241 11/1962 Palmer 315/99 [33] ga sePH3'1968 3,325,682 6/1967 Elliott 315/97 78,724 4 1968 K d 311 43/16650,43/45727,43/53047,43/75413 3 3 I 5/97 and 43/79818 Primary Examiner-Eli Lieberman AttorneyStevens, Davis, Miller & Mosher [54] FLUORESCENT LAMP DEWCE WITH ABSTRACT: A fluorescent lamp device in which a DC power P source of high voltage and small capacity is connected for mg maintaining a slight glow discharge within the lamp, a main [52] U.S.Cl 315/171, current of the lamp being adjustably supplied from a main 343/176 power source of large capacity and a rectifier is inserted into [51] Int. (ll 1105b 37/00, the main power circuit for blocking high voltages DC current H05!) 41/00 flowing into the main circuit from the high-voltage source.

SUPPL Y PAIENIEDSEP 7I97I 3.603.841

SUPPL Y INVENTORS MEI/719 9/9/19), hams, 3.04145 Kazan/am mm:

ATTORNEY 5 FLUORESCENT LAMP DEVICE WITH LUMINOSITY CONTROL This invention relates to fluorescent lamp devices and more particularly to a device of the kind described whose luminous intensity is adjustable so as to used as a display device, indication device, cinesign or the like.

In a display device or the like, it is required that the intensity of its light source is freely variable over a wide range. Fluorescent lamps are suitable for the purpose of display since they can emit light of various colors with a high luminous efficiency. However, the fluorescent lamp is defective in that its luminous intensity is difficult to vary freely. Various attempts have hitherto been made in order to vary the luminous intensity of the fluorescent lamp or rather to provide means for the dimming thereof.

Among various devices for the purpose is the provision in which a high-voltage power source of small capacity is cnnectedto the lamp through a high resistance in addition to a main power circuit for maintaining a slight discharge in the lamp. Such a device has an advantage in that the light intensity of the lamp can be controlled over a wide range without any extinction of the light by virtue of the auxiliary high-voltage power source. However, such a conventional device simultaneously has a disadvantage in that the auxiliary high-voltage source makes current flow into the main power source and thereby the main power source might be broken or the highvoltage source might be subjected to an internal voltage drop which causes the slight discharge in the lamp to be extinguished. For obviating the above defects, another conventional device is provided with two divided electrodes, one of which is connected to a high-voltage source and the other is connected to a main power circuit. However, this device has a disadvantage in that the high-voltage source should be disconnected from the lamp by means of a thermal switch after lighting and thereby the device is not only complicated, but cannot be provided with a control means over a wide range.

It is therefore, a primary object of the present invention to provide a fluorescent lamp device of the kind preferably used as a display device, indication device, cinesign or the like, in which the light intensity is easily, smoothly and rapidly variable over a wide range from a low luminous intensity to a high luminous intensity, which is simple in structure and inexpensive, and which can operate with a high power utilization efficiency.

The fluorescent lamp device of the present invention which attains the above object comprises a fluorescent lamp including a glass envelope, mercury and rare gas contained in small amounts within said glass envelope, a phosphor coating provided on the inside wall of said glass envelope a preheated cathode hermetically sealed in one end of said glass envelope, and at least one anode hermetically sealed in the other end of said glass envelope, a preheating power source for continuously supplying a current tosaid preheated cathode to heat the same, a direct current power source of high voltage and small capacity connected through a high resistance between said anode and said cathode for maintaining a very slight glow discharge within said envelope, and a main power source capable of supplying tosaid anode a current which is variable depending on a signal.

The high resistance described above has preferably such a value that a very small current of the order of 0.1 to 1 ma. can flow through the tube. When the current value is more than 1 ma., the luminescence emitted from the tube due to the above current restricts the lower limit of the adjustable luminous intensity, while when the current value is less than 0.] ma., the drop in tube voltage is insufficient and the main power source must have a correspondingly high voltage. Further, the tube is preferably provided with two anodes with a spacing of more than 3 mm. between the anodes. A spacing of the order of mm. will be sufficient for a fluorescent lamp of conventional size.

Some embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which:

FIG. I is a partly cutaway front elevational view of a fluorescent lamp in the fluorescent lamp device embodying the present invention and a connection diagram of an electrical circuit for energizing the fluorescent lamp;

FIG. 2 is a view similar to FIG. I, but showing the structure of another embodiment of the present invention; and

FIG. 3 is a view similar to FIG. 2, but showing a further embodiment of the present invention.

Referring to FIG. 1, a fluorescent [lamp 1 of conventional size is rated at l0 w. and comprises an elongated glass bulb having an outside diameter of 25 mm. A phosphor coating (not shown) is provided on the inner surface of the glass bulb, and argon and mercury are enclosed within the glass bulb. An electrode 2 is hennetically sealed in one end of the glass bulb, while two electrodes 3 and 3' are hermetically sealed in the other end of the glass bulb. The electrode 2 is in the form of a coil filament. A current is continuously supplied from a power source 4 to the electrode 2 to heat the same so that the electrode 2 acts as the preheated cathode. The other electrodes 3 and 3 are spaced apart at 5 mm. from each other and are electrically insulated from each other within the glass bulb. A direct current power source 6 of 400 volts is connected between the electrode 3 and the cathode 2 through a high resistance 5 of 2.5 megohms. A series connection including a variable resistance 7, a main direct current power source 8 of 70 v. and a switch 9 is connected between the electrode 3' and the cathode 2. The rectifier 10 is disposed in the main power source circuit in such a polarity as to block the flow of current from the power source 6 and to allow passage therethrough of a current flow from the power source 8. In such a provision, the main power circuit including the rectifier 10 is not directly impressed with a high voltage from the direct current highvoltage source 6, and thereby the elements in the power circuit is hardly caused to be broken. Even if the gap between the electrodes 3 and 3 becomes conductive, the main power source can be protected by the rectifier l0. intensity to a high luminous intensity. In other embodiments, experiments also proved that the voltage of the main power source which is les than twice the tube voltage was quite sufficient.

Another embodiment shown in FIG. 2 is generally similar to the embodiment shown in FIG. 1 except that the former comprises a single anode 3. In FIG. 2, a power source 6 and a main power source 8 are both connected to the single anode 3. In the case of the embodiment shown in FIG. 2, a rectifier I0 is disposed in the main power source circuit in such a polarity as to block the flow of current from the power source 8. By virtue of the provision of the rectifier 10, an undesirable flow of current from the high-voltage power supply 6 to the circuit in cluding the main power source at low voltage does not occur, and the current from the main power source 8 can freely pass through the tube once a very slight glow discharge takes place within the tube to reduce the voltage across the electrodes 2 and 3. Thus, only one anode sufiices.

A further embodiment shown in FIG. 3 is generally similar to the embodiment shown in FIG. 2 except that a transistor 1 l is disposed in place of the variable resistance. The emitter of the transistor 11 is connected to the cathode 2 of the fluorescent lamp 1 through a main power source 8, while the collector thereof with the anode 3 of the fluorescent lamp 1 through a rectifier 10. The base current of the transistor II is finely regulated by a circuit including a battery 12 and resistances I3 and 13'. The base of the transistor I 1 may be connected with a source of desired electrical signal supply for varying the luminous intensity of the fluorescent lamp depending on a variation in the signal. In lieu of the transistor, the main power source circuit may include a thyristor therein. Furthennore, in lieu of the direct current power source an alternate current power source may be used as a main power source.

What is claimed is:

l. A fluorescent lamp device whose luminous intensity is freely adjustable comprising a fluorescent lamp including a glass envelope, mercury and rare gas contained in small amounts within said glass envelope, a phosphor coating provided on the inside wall of said glass envelope, a preheated cathode hermetically sealed in one end of said glass envelope, and at least one anode hermetically sealed in the other end of said glass envelope, a preheating power source for continuously supplying a current to said preheated cathode to heat the same, a direct current power source of high voltage and small capacity connected through high resistance between said cathode and said anode for maintaining a very slight glow discharge within said envelope, and a main power source capable of supplying to said anode a current which is variable depending on a signal, and a rectifier disposed in the circuit connecting said main power source with said anode in such a polarity that it allows passage therethrough of current from said main power source but blocks flow of current from said direct current power source for maintaining the very slight glow discharge.

2. A fluorescent lamp device as claimed in claim 1, in which a current in the range of 0.1 to 1.0 ma. normally flows between said cathode and said anode for maintaining said very slight glow discharge.

3. A fluorescent lamp device as claimed in claim 1, in which the main power source circuit comprises a transistor.

4. A fluorescent lamp device as claimed in claim 2, in which the main power source circuit comprises a transistor. 

1. A fluorescent lamp device whose luminous intensity is freely adjustable comprising a fluorescent lamp including a glass envelope, mercury and rare gas contained in small amounts within said glass envelope, a phosphor coating provided on the inside wall of said glass envelope, a preheated cathode hermetically sealed in one end of said glass envelope, and at least one anode hermetically sealed in the other end of said glass envelope, a preheating power source for continuously supplying a current to said preheated cathode to heat the same, a direct current power source of high voltage and small capacity connected through high resistance between said cathode and said anode for maintaining a very slight glow discharge within said envelope, and a main power source capable of supplying to said anode a current which is variable depending on a signal, and a rectifier disposed in the circuit connecting said main power source with said anode in such a polarity that it allows passage therethrough of current from said main power source but blocks flow of current from said direct current power source for maintaining the very slight glow discharge.
 2. A fluorescent lamp device as claimed in claim 1, in which a current in the range of 0.1 to 1.0 ma. normally flows between said cathode and said anode for maintaining said very slight glow discharge.
 3. A fluorescent lamp device as claimed in claim 1, in which the main power source circuit comprises a transistor.
 4. A fluorescent lamp device as claimed in claim 2, in which the main power source circuit comprises a transistor. 